1. Field of the Invention
The invention relates to a flame-resistant spun staple yarns, and fabrics and garments comprising these yarns, and methods of making the same. The yarns have 60 to 85 parts by weight of polyoxadiazole staple fiber and 15 to 40 parts by weight modacrylic staple fiber; based on the total amount of the polyoxadiazole staple fiber and modacrylic staple fiber in the yarn.
2. Background of the Invention
Industrial workers and others that can be exposed to flames, high temperatures, and/or electrical arcs and the like, need protective clothing and articles made from thermally resistant fabrics. Any increase in the effectiveness of these protective articles, or any increase in the comfort or durability of these articles while maintaining protection performance, is welcomed.
Fabrics made from 100% polyoxadiazole fiber generally are deemed to have good thermal resistance because such fabrics, when tested, have a limiting oxygen index in excess of 21, meaning that they will not sustain a flame in air. Further, freshly made 100% polyoxadiazole fiber fabrics can have an acceptable char length, which is 4 inches or less, when determined in accordance with ASTM D-6413-99 “Standard Test Method for Flame Resistance of Textiles (Vertical Method)”, also known as the “Vertical Flame Test”. Such fabrics are used in clothing that is repeatedly exposed to a cycle of wearing and washing, and it has been found that after a number of washings, in some fabrics the vertical flame performance deteriorates, but enough that it can fail the vertical flame test; that is, the fabric has a char length in excess of 4 inches. It has been speculated that this may be due to the fabrics becoming more “fluffy” after numerous washings. What is needed, therefore, is to provide a margin of improvement in the thermal performance of fabrics containing polyoxadiazole fibers to offset any such deterioration in vertical flame properties after washings.